// 代码索引 3-10-3-1
#include <iostream>
#include <Eigen/Dense>

using namespace std;
using namespace Eigen;

int main()
{
    int data[] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
    Map<RowVectorXi> v(data, 4);
    cout << "The mapped vector v is: " << v << "\n";
    new (&v) Map<RowVectorXi>(data + 4, 5);
    cout << "Now v is: " << v << "\n";

    return 0;
}